How do I get my nested loop function to iterate through the entire (at least 2) list variables and append to a new list output?

Question

I'm trying to write a function that takes 2 list variables ie first_names and last_names .

I'm using a nested for loop in my function to iterate through both lists and append the values to return a new 'combined' variable list.

The function takes the two list parameters but iterates through just the first index value [0] of each list and outputs that - the loop ends.

first_names = ["Dave", "James", "Steve"]

last_names = ["Smith", "Jones", "Jackson"]

def NameCombine(first_names,last_names):
    combined = []
        for first in first_names:
            for last in last_names:
                combined.append(first+last)
                return combined

print(NameCombine(first_names,last_names))

Expected output: DaveSmith, JamesJones, SteveJackson

Actual output: DaveSmith

I'm expecting a new combined list of both the first and last name at each index.

But it's returning the first two values of each list and then the loop ends.

Answer 1

You can combine them with zip within comprehension:

def NameCombine(first_names,last_names):
    return [a+b for a, b in zip(first_names, last_names)]

Answer 2

You may try with this code.

first_names = ["Dave", "James", "Steve"]

last_names = ["Smith", "Jones", "Jackson"]

def NameCombine(first_names, last_names):
    combined = []
    for i in range(0, len(first_names)):
        if last_names[i] != None:
            combined.append(first_names[i] + " " + last_names[i])
        else:
            combined.append(first_names[i])
    return combined

print(NameCombine(first_names,last_names))

Answer 3

The pythonic and list comprehension is my preferred way. But if you really wanted a solution using a nested loop, this would work for you. Just used your code and added an additional condition to only print the desired result.

The results from this solution are: ['DaveSmith', 'JamesJones', 'SteveJackson']

first_names = ["Dave", "James", "Steve"]

last_names = ["Smith", "Jones", "Jackson"]

def NameCombine(first_names,last_names):
  combined = []
  for first in first_names:
    for last in last_names:
      if first_names.index(first) == last_names.index(last):
        combined.append(first+last)
  return combined

print(NameCombine(first_names,last_names))

Answer 4

Since most of them here answer specifically to your question. I would like to add the other way of achieving the solution to this problem as below,

here I used map and add from operator module

list(map(operator.add, first_names, last_names))
# ['DaveSmith', 'JamesJones', 'SteveJackson']